Use of Surface Desander to Bring Back Subsea Production. How to Overcome Reservoir, Well and Facilities Challenges

A subsea well in Deepwater field in Malaysia observed high sand production during the first half of 2019, this well had been on production for around 7 years. Further evaluation during the second half of 2019 determined that the downhole sand control had been compromised and the well would require intervention to bring back its locked in potential. Technical and Economical evaluations were conducted to determine the most feasible well restoration activity. This paper covers the aspects from technology selection to operation challenges and identified solutions. Riserless well intervention was initially identified to restore production from this well and compared with other alternatives. After technical and economical evaluations, the use of a surface desander was identified as the best solution to unlock production from this well while a more permanent solution was evaluated. A surface desander was installed upstream of first stage separation. Well and facilities operating envelopes were updated to determine the operating window for the well as per last observed conditions before the well was shut in. However, once the well was back online a much higher than anticipated watercut was observed and different solutions, in term of surface settings, were tested to determine a new operation window. The use of surface desander to handle subsea sand control failure requires a steady flow against a significant choke to the flowline at the end of the riser. Changes in reservoir watercut provided a significant challenge to flow the well at steady conditions and limited the efficacy of surface desander. Flow assurance is a key parameter to avoid sand deposition along the subsea flowline to the platform. Use of a neighbor well proved to allow continuous steady production and a new logic was designed to maximize production from both wells while keeping sand from reaching the production facilities.